Tonight may be the eve of the first day of the Islamic new year, but don’t expect to see any wild parties.

This year, Saturday marks the first of Muharram, the first month of the Islamic calendar.

Divided into 12 months of 29 or 30 days each, the Islamic calendar varies from the commonly used Gregorian calendar. It is a lunar calendar with 11 fewer days than a regular year. Because of this, the months fall at different seasons during the year and take about 33 years to get back to where they started.

Muharram is considered the second most important fasting season after Ramadan, the ninth month in the Islamic calendar.

“It is an important month among Muslims,” said Riaz Hasan, former outreach director for the Tracy Islamic Center.

But not all Muslims observe Muharram in the same ways.

Sunni Muslims, the largest sect in Islam, recall the migration of Muslims from Mecca to Medina that marked the beginning of the calendar. Many Sunnis also observe the voluntary fasting on Ashura, the 10th day of Muharram.

Ashura is a day the Prophet Muhammad fasted and some Muslims extend the fast for two days. Although voluntary, the Ashura fast is considered good to do.

“Because the prophet did it, you want to follow in his footsteps,” Hasan said.

Hasan and his wife, Rukhsana, are Sunni Muslims who observe these Muharram traditions as a way to be more spiritual. In addition to fasting, extra prayers are said at this time along with reading the Quran.

Shiite Muslims observe another part of Muharram. This is a time of mourning for Shiites, who commemorate the martyrdom of Hazrat Imam Hussain, the grandson of Muhammad.

At a time when the Muslim population was growing, there was a battle over who would become the new leader. In the battle, Hussain was massacred with his fighters in what is now Iraq.

During this time of mourning, bright colors are not worn, and marriages and other celebrations are not permitted.

Sunnis remember the event as a tragedy, but do not try to relive the battle each year.

Violent police encounters in California last year led to the deaths of 157 people and six officers, the state attorney general’s office said Thursday in a report that provides the first statewide tally on police use-of-force incidents.

At 6:03 p.m. Wednesday, police responded to reports of the robbery at the facility, 2301 Bancroft way, and learned that a man who snuck into the facility and began prowling through the building, taking cell phones and wallets from victims.

Investigators’ efforts to solve the case led to the arrests of Pablo Mendoza, 25, of Hayward, Brandon Follings, 26, of Oakland and Valeria Boden, 26, of Alameda, the Alameda County Sheriff’s Office said Thursday.